The present invention relates to data storage and retrieval systems, and more particularly to a suspension system having a particle capture device.
Hard Disc Drives (HDDs) are well known in the art and comprise a housing that contains a storage medium and a suspension assembly. Generally the storage medium is in the form of one or more rotatable discs, each disc having numerous concentric data tracks on each side of the disc for storing data in the form of localized magnetic fields. When multiple discs are used, a stack is formed of coaxial discs having generally the same diameter. This stack is connected to a spindle, which can rotate the discs simultaneously.
The suspension assembly includes an actuator arm and a head gimbal assembly (HGA), which support and position a transducing head over the disc. The transducing head is used to read and/or write to the data tracks. The transducing head is supported by the HGA, which, in turn, is supported by the actuator arm.
The actuator arm is rigid and rotatable about an axis. A large scale arm actuation motor, such as a voice coil motor (VCM), is used to rotate the actuator arm about an axis. The VCM moves the arm when electrical signals are sent to a VCM coil attached to the actuator arm. The signals induce movements with respect to fields created by permanent magnets located in the HDD housing. A plurality of actuator arms disposed next to a stack of discs may be connected to a common E-block, which allows common rotation of the actuator arms.
A standard HGA comprises a base plate, a load beam, a gimbal, a flexible interconnect circuit, and a slider. The load beam provides the main support structure for the HGA. The load beam is connected to the base plate, and the base plate is swaged to the actuator arm. Opposite the base plate, the load beam is connected to the gimbal. The gimbal and base plate are each attached to the load beam by methods known to the art, such as spot welding. Alternative HGA configurations have two base plates connected to opposing sides of the load beam. Still other HGA configurations have no base plate, and the load beam is attached directly to the actuator arm.
The load beam and the actuator arm generally have one or more openings along their length. These openings reduce the amount of material used in constructing the load beam and the actuator arm, thereby reducing the mass of the suspension assembly. Reduction of the mass of the suspension assembly facilitates positioning the HGA above a selected data track on the disc by lessening the load moved by the VCM.
The HGA is positioned relative to a surface of the disc. To better position the HGA near the surface of the disc, the load beam is typically bent towards the disc. This positions the gimbal and slider closer to the surface of the disc than if the load beam extended straight from the actuator arm.
Furthermore, the HGA is movably positioned above different tracks located between an outer diameter and an inner diameter of the disc. The rotational movement of the actuator arm allows the attached HGA to make arc-shaped movements relative to the disc. These arc-shaped movements allow quasi-radial positioning of the HGA to access selected data tracks on the disc.
The slider is the portion of the HGA positioned over a selected data track of the disc. The slider is supported by the gimbal. The gimbal is designed to flex, allowing the slider to follow the surface of the disc more closely then if the slider were mounted directly on the load beam. The flexure of the gimbal thus provides a biasing force to position the slider close to the disc. The slider carries a transducing head for reading and/or writing to the selected data track. The transducing head may include a magnetoresistive (MR) read element as well as a write coil.
The flexible interconnect circuit electrically connects the transducing head with components located on or near the actuator arm. Leads and traces on the flexible interconnect circuit allow electronic signals to travel from the transducing head to a pre-amp that amplifies the minimal signal from the head so the disc drive can read the data signal.
In operation, rotation of the disc produces an airflow that generally co-rotates with the disc. The aerodynamically shaped slider has an air bearing surface (ABS). The interaction of the airflow and the ABS causes the slider to “fly” a small distance above the surface of the disc on a cushion of air. At the same time, the biasing force provided by the gimbal holds the slider near the disc surface. Thus, the transducing head is held a substantially constant distance above the surface of the disc for reading and/or writing to the data tracks.
While efforts are made to prevent contaminants from entering the HDD housing during fabrication and operation, particles or other contaminants can be present in airflows. Hence, airflow along the load beam may carry one or more particles. These particles can attach themselves to portions of the HGA, thereby contaminating surfaces of the HGA. Such contamination is undesirable. In particular, a down-beam airflow may travel along the length of the load beam carrying particles. The particles may collect on portions of the slider and/or the gimbal. Over time, the particles that have collected on the slider or gimbal can migrate, influenced by gravity, windage, operating shock, and/or shock vibration, to the ABS. Contamination of the ABS interferes with the operation of the HDD. Debris on the ABS, in the form of built up particle contamination, can cause unstable slider flight. Contamination of the ABS can also reduce or destroy the functioning of the transducing head. Additionally, contaminates on the ABS can act as an abrasive that scratches the magnetic layer of the disc, thereby destroying the capacity for the disc to retain data. Therefore, contamination of the ABS can lead to errors in the operation of the HDD.
Known in the art are recirculating (or recirculation) filters placed in the HDD housing to collect airborne particles. Such recirculating filters are provided within the HDD housing away from the suspension assembly. For example, Beecroft, U.S. Pat. No. 5,406,431, teaches a recirculating filter disposed in a HDD housing on an opposite side of the disc from the actuator arm assembly. While a recirculating filter can remove some particles present in HDD airflows, such a recirculating filter is located far from the HGA. Thus, the recirculating filter may not eliminate contamination of the ABS because airflow containing particulate contaminants may contact the HGA before the airflow passes through the recirculating filter.
Other known systems attempt to reduce contamination of the ABS without providing a filter. One example is a gimbal tongue shaped to direct particles away from the slider in order to avoid contaminant buildup on the HGA. However, such a design does not include a means for capturing the particles to reduce the number of particles traveling near the HGA, where the particles can attach themselves and potentially migrate to the ABS.
Another problem encountered in prior HDD designs is excitation of the HGA due to asymmetric airflows. As rotation of the disc generates an airflow co-rotating with the disc, the airflow pattern is generally symmetrical. However, as the airflow travels near the load beam, the openings in the load beam may generate turbulence in the form of eddies, periodic spiral vortices, or other asymmetric airflow patterns. These asymmetric airflows exists in three dimensions, and can influence airflows in a wake region, the wake region being adjacent to and downstream of the load beam. This turbulence generated by the airflow at the openings on the load beam can cause excitation of the load beam, and in turn, excitation of the entire HGA. Undesirable off-track movements can result from excitation of the HGA, leading to drive errors. It is well-known that a structure with no holes performs better in regards to windage excitation due to the reduction or elimination of eddies around the openings. However, elimination of mass-saving holes on the load beam is undesirable because it increases the mass of the load beam.
Thus, a suspension assembly is needed to reduce errors in HDD systems by reducing windage-induced vibrations in the HGA without significantly increasing the mass of the HGA, and by capturing particles carried by airflow along the HGA.